1. Field of the Invention
The present invention relates to a cleaning liquid composition used for cleaning a semiconductor substrate and, in particular, it relates to a cleaning liquid composition suitable for removing particulate contamination and metallic contamination adsorbed on the surface of a hydrophobic substrate such as bare silicon or a low dielectric constant (Low-K) film.
2. Description of Related Art
Accompanying the increasing integration of ICs, there is a demand for strict contamination control since trace amounts of impurities greatly influence the performance and yield of a device. That is, strict control of particulate contamination and metallic contamination on a substrate is required, and cleaning with various types of cleaning liquids is therefore carried out at each step in semiconductor production.
With regard to cleaning liquids generally used for semiconductor substrates, ammonia-hydrogen peroxide-water (SC-1), which is an alkaline cleaning liquid, is used for removing particulate contamination, and sulfuric acid-hydrogen peroxide, hydrochloric acid-hydrogen peroxide-water (SC-2), dilute hydrofluoric acid, etc., which are acidic cleaning liquids, are used for removing metallic contamination, and the cleaning liquids are used singly or in combination according to the intended purpose.
On the other hand, accompanying advances of the increasing integration of ICs and making them with multilayer wiring structures, the substrate surface is required to be made more strictly planar in each process, and as a new technique the chemical-mechanical polishing technique (hereinafter called CMP) has been introduced into the semiconductor production process. In this technique, the surface of the substrate is polished and planarized by means of a rotating buff while supplying a mixed slurry of abrasive particles and a chemical agent. At the same time, materials constituting the surface of the substrate that is planarized have been changing. As a result, post-CMP substrate surfaces are contaminated by particulate contamination originating from alumina or silica contained in the abrasive and various types of metallic contamination originating from the constituents of the surface that is polished and the chemical agent contained in the slurry. In order to remove this contamination, brush-cleaning, which involves both the chemical effect of a cleaning liquid and the physical effect of brushing, is carried out as general post-CMP cleaning, and as the cleaning liquid used here an appropriate cleaning liquid is selected from various types of cleaning liquids while taking into consideration the properties of the constituents of the surface of the substrate and the contamination.
In the case where the surface of a substrate to which CMP is applied is a conventional SiO2 interlayer insulating film, two stage cleaning has been carried out, and this employs the alkaline cleaning liquid for removing particulate contamination and the acidic cleaning liquids for removing metallic contamination.
However, in the case of interlayer insulating films used in recent years, in which a metal material such as Cu or W is exposed as a via-hole or a wiring material, the acidic cleaning liquids will corrode the metal material or are unable to remove the metallic contamination adequately within a time in which no corrosion occurs. The alkaline cleaning liquids also cause problems such as corrosion of Cu. As a method for solving these problems, an aqueous solution containing an organic acid and a complexing agent has been proposed as a cleaning liquid for metallic contamination (JP, A, 10-72594 and JP, A, 11-131093), and a cleaning liquid containing an organic acid and a complexing agent has been proposed as a technique for simultaneously removing metallic contamination and particulate contamination (JP, A, 2001-7071).
Furthermore, in recent years attempts have been made to use, as interlayer insulating films, an organic film such as an aromatic aryl polymer (SiLK, Dow Chemical) having lower dielectric constant than that of the conventional SiO2 system, a silicon-based film such as MSQ (Methyl Silsesquioxane), HSQ (Hydrogen Silsesquioxane) or SiOC (Black Diamond, Applied Material) and, furthermore a porous silica film having low dielectric constant. It is known that these Low-K film materials are strongly hydrophobic, and it has been reported in recent research that when a cleaning liquid having poor wettability toward the surface of a film is used in brush-cleaning, the brush-cleaning does not work effectively and the removal of particulate contamination is inadequate, and since the above-mentioned cleaning liquids have poor wettability toward the Low-K films, the films cannot be cleaned sufficiently. Under such circumstances, the present sinventors have proposed an aqueous solution containing an aliphatic polycarboxylic acid and a surfactant as a post-CMP cleaning liquid composition that has good wettability toward an interlayer insulating film formed from a Low-K film, etc., and can be used for the removal of particulate contamination and metallic contamination (Japanese Patent Application 2002-41393).
However, in subsequent research it has been found that, depending on the combination of the surfactant and the Low-K film, there is the defect that the surfactant might be adsorbed on the surface of the Low-K film or penetrate the Low-K film, thus damaging the Low-K film such as, for example, changing the refractive index.
Moreover, as an analogous organic acid-containing composition, a composition containing an organic acid, water, and an organic solvent has been disclosed (JP, A, 2002-206709), and after the application of the present invention, a composition containing an organic acid, water, an organic solvent and an anticorrosive has been disclosed (US2003/0130147A1). However, these techniques relate to a resist stripping agent, and post-CMP removal of particulate contamination and metallic contamination has not been disclosed.
Furthermore, after the application of the present invention, a cleaning liquid composition for semiconductor substrate having a Low-K film, containing an organic acid, water, and an ethylene-oxide-type surfactant as essential components, which may further contain alkyl alcohol has been disclosed (WO03/065433A1). However, all the examples are compounds containing an organic acid, water and a surfactant, and they have a possibility to damage Low-K films similar to those disclosed in Japanese Patent Application 2002-41393.